LiDAR DEVICE AND METHOD OF OPERATING THE SAME

ABSTRACT

Provided are a LiDAR device and a method of operating the LiDAR device. The LiDAR device includes a light-emitting unit configured to emit modulated light onto an object, a light-receiving unit configured to receive the modulated light reflected by the object, a computation unit configured to calculate a distance to the object based on a reception signal of the modulated light provided by the light-receiving unit, a modulation unit configured to provide a modulation signal to the light-emitting unit to generate the modulated light, and a controller configured to control operations of at least one of the light-emitting unit, the light-receiving unit, the computation unit, and the modulation unit.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 15/870,005, filedJan. 12, 2018, which claims priority from Korean Patent Application No.10-2017-0106253, filed on Aug. 22, 2017, in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND 1. Field

Apparatuses and methods consistent with exemplary embodiments relate todistance measuring devices, and more particularly, to light detectionand ranging (LiDAR) devices and methods of operating the LiDAR devices.

2. Description of the Related Art

Three-dimensional (3D) LiDAR devices for capturing 3D images may be usedin a sensor for an autonomous vehicle or a motion capture sensor of auser interface. The 3D LiDAR device may be used in a depth camera fordetecting depth information, a military laser radar, that is, a LADAR,or a range sensor for robot navigation.

SUMMARY

One or more exemplary embodiments may provide LiDAR devices having acrosstalk prevention function.

One or more exemplary embodiments may provide methods of operating theLiDAR devices.

Additional exemplary aspects will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the presented exemplaryembodiments.

According to an aspect of an exemplary embodiment, a light detection andranging (LiDAR) device includes: a modulation unit configured to outputa modulation signal; a light-emitting unit configured to generatemodulated light based on the modulation signal and to emit the modulatedlight onto an object; a light-receiving unit configured to receive themodulated light reflected by the object and generate a reception signal;a computation unit configured to calculate a distance to the objectbased on the reception signal; and a controller configured to controloperations of at least one of the light-emitting unit, thelight-receiving unit, the computation unit, and the modulation unit.

The modulated light may include a modulated single light pulse.

The modulated light may include a modulated light pulse group, and themodulated light pulse group may include a plurality of modulated singlelight pulses.

The modulation unit may include a light modulation device.

The computation unit may include a time-to-digital converter (TDC).

The modulated single light pulses may have pulse widths that aredifferent from each other, and a ratio between the widths may beconstant.

Gaps between the modulated single light pulses may be equal to ordifferent from each other.

According to an aspect of another exemplary embodiment, a method ofoperating a LiDAR device includes: modulating light to be emitted;emitting modulated light onto an object; receiving the modulated lightreflected by the object; measuring a time difference between a time atwhich the modulated light is emitted and a time at which the modulatedlight is received; and computing a distance to the object using themeasured time difference.

The modulating of the light to be emitted may include applying a lightemission start signal to a light-emitting unit; and applying amodulation signal to a modulation unit connected to the light-emittingunit.

The modulating of the light to be emitted may include modulating a widthof the light to be emitted.

The time difference may be measured by using a TDC.

The modulated light may include a modulated single light pulse having afirst cycle or a modulated light pulse group having a second cycle,where the modulated light pulse group may include a plurality ofmodulated light pulses.

The modulating of the width of the light to be emitted may beimplemented by using a randomly generated look-up table, and a pluralityof different LiDAR device may include look-up tables having differentsequences from each other.

The modulating of the width of the light to be emitted may beimplemented by using a unique value assigned to the LiDAR device as aparameter for modulating the width of the light pulse. The unique valuemay be a signal of a global positioning system (GPS) with respect to theLiDAR device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other exemplary aspects and advantages will becomeapparent and more readily appreciated from the following description ofexemplary embodiments, taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a block diagram showing a LiDAR device according to anexemplary embodiment;

FIG. 2 shows a single light pulse before modulation, the single lightpulse emitted from a light-emitting unit of FIG. 1;

FIG. 3 shows a pulse group including a plurality of light pulses beforemodulation, the pulse group including a plurality of light pulsesemitted from the light-emitting unit of FIG. 1;

FIG. 4 shows a single light pulse having a width that is modulated byapplying a modulation signal to the single light pulse of FIG. 2;

FIG. 5 shows light pulses modulated through application of a modulationsignal to the light pulse of FIG. 3;

FIG. 6 shows a magnified view of a first modulated light pulse groupMPG1 of FIG. 5 that is modulated;

FIGS. 7A and 7B show magnified views of the first light pulse group MPG1that is modulated, when the first light pulse group PG1 of FIG. 3includes three light pulses;

FIG. 8 is a time chart showing time delays (or time differences) betweena light pulse emitted from the light-emitting unit of FIG. 1 and amodulated light pulse received by a light-receiving unit after the lightpulse has been reflected by an object; and

FIG. 9 is a flowchart for explaining a method of operating a LiDARdevice, according to an exemplary embodiment.

DETAILED DESCRIPTION

A three-dimensional light detection and ranging (3D LiDAR) deviceaccording to an exemplary embodiment applies modulation to light to bemade incident on an object and shares information of the modulation ofthe light with a light-receiving unit. Accordingly, although a varietyof light is received, the light-receiving unit generates informationwith respect to only light emitted from the light-emitting unit. Bycontrolling a modulation degree of a light pulse of each of a number ofLiDAR devices, each of the LiDAR devices may use a unique type of lightpulse, and as a result, although the LiDARs devices are simultaneouslyused in the same space, crosstalk between the LiDAR devices may beprevented.

Hereinafter, LiDAR devices according to the present disclosure andmethods of operating the LiDAR devices will be described in detail withreference to the accompanying drawings. In the drawings, thicknesses oflayers or regions may be exaggerated for clarity of explanation.

FIG. 1 is a block diagram of a LiDAR device 100 according to anexemplary embodiment.

Referring to FIG. 1, the LiDAR device 100 may include a light-emittingunit 110 configured to emit light to an object 105, a modulation unit120, a light-receiving unit 130 configured to receive light reflected bythe object 105, a computation unit 140 configured to perform acomputation operation for obtaining a distance to the object 105, and acontroller 150 configured to control operations of each element of theLiDAR device 100. The object 105 may be a fixed object (hereinafter, afixed body). Alternately, the object 105 may be an object capable ofmoving or a moving object (hereinafter, a moving body). The object 105may be a natural object or an artificial object. The definitions of thefixed body and the moving body may vary according to whether the LiDARdevice 100 itself is fixed or moving. The light-emitting unit 110 mayinclude a light source 110A configured to emit light towards the object105. Light emitted from the light-emitting unit 110 towards the object105 may be light of a pulse type (hereinafter, a light pulse). The lightpulse may be periodically emitted. The light pulse may be, for example,a laser pulse. The light source 110A included in the light-emitting unit110 may include, for example, a laser diode. The modulation unit 120 isconnected to the light-emitting unit 110 and the controller 150. Themodulation unit 120 may be configured to transmit a modulation signal tothe light-emitting unit 110 to be applied to the light emittedtherefrom. The modulation unit 120 may be directly connected to thelight source 110A of the light-emitting unit 110. The modulation signalfrom the modulation unit 120 applied to the light emitted from thelight-emitting unit 110 may be generated by using a randomly generatedlook-up table (LUT). Alternately, the modulation signal may be generatedby using a unique value or a signal assigned to the LiDAR device 100. Inthis way, a unique modulation operation may be possible for each of aplurality of LiDAR devices 100, and thus, the light pulse generated byeach of the LiDAR devices 100 may have a unique pattern. Accordingly,crosstalk between the LiDAR devices 100 may be prevented. The modulationunit 120 may include a light modulation device. The light-receiving unit130 is connected to the computation unit 140. The light-receiving unit130 receives light reflected by the object 105 to generate an electricalsignal. The electrical signal generated by the light-receiving unit 130is transmitted to the computation unit 140. The light-receiving unit 130includes a photoelectric conversion device, for example, a photodiode,but the present exemplary embodiment is not limited thereto. Thecomputation unit 140 may include a time-to-digital converter (TDC). Thecomputation unit 140 may calculate a time delay of light based on anelectrical signal received from the light-receiving unit 130 by using aTDC, and may thereby compute a distance from the LiDAR device 100 to theobject 105. The time delay may denote a time difference between a timewhen light is emitted towards the object 105 from the light-emittingunit 110 and a time when the light reflected by the object 105 isreceived by the light-receiving unit 130. The operation of emittinglight from the light-emitting unit 110 is controlled by the controller150. The controller 150 may simultaneously transmit a light emissionstarting signal to the light-emitting unit 110 and the computation unit140. In this way, the computation unit 140 may know a light emissionstarting time of the light-emitting unit 110. Also, since thecomputation unit 140 may know a light reception time of thelight-receiving unit 130 based on an electrical signal provided by thelight-receiving unit 130, the computation unit 140 may calculate thetime delay. The computation unit 140 receives information from thecontroller 150 regarding a modulated light pulse emitted from thelight-emitting unit 110. Based on the information, from light receivedby the light-receiving unit 130, the computation unit 140 calculates atime delay with respect to only the modulated light pulse emitted fromthe light-emitting unit 110, and may perform a distance computationoperation with respect to the object 105. Distance information obtainedfrom the computation operation of the computation unit 140 istransmitted to the controller 150. The controller 150 may controloperations of other elements, that is, the modulation unit 120, thelight-receiving unit 130, and the computation unit 140, through theoperation of the light-emitting unit 110. The controller 150 may includea central processing unit. The controller 150 may include a personalcomputer (PC). The LiDAR device 100 may be applied to any of variousfields, for example, autonomous devices, such as vehicles or drones,depth cameras, robot navigations, and military and medical fields. Theconfiguration of the controller 150 may vary according to the field ofapplication.

FIG. 2 shows a single light pulse before modulation, emitted from thelight-emitting unit 110 of FIG. 1. FIG. 3 shows a plurality of lightpulses before modulation, emitted from the light-emitting unit ofFIG. 1. For convenience, hereinafter, the light pulses are depicted withrectangular pulse shapes, though the light pulses may have a sine waveshape.

According to the present exemplary embodiment, as depicted in FIG. 2,light pulses P1 and P2 are light pulses before modulation that areemitted according to a first cycle T1 and have a first width W1. Each ofthe light pulses P1 and P2 is a single light pulse.

According to another exemplary embodiment, as depicted in FIG. 3, firstand second light pulse groups PG1 and PG2 may be emitted beforemodulation and are emitted according to a second cycle T2. The first andsecond light pulse groups PG1 and PG2 may have the same configurationsand characteristics as each other. The first light pulse group PG1 mayinclude first and second light pulses PA1 and PA2 that togetherconstitute a train signal. The first and second light pulses PA1 and PA2are separated by a first distance d1. The first and second light pulsesPA1 and PA2 may have the same height and respectively have a secondwidth W2 and a third width W3. The second width W2 of the first lightpulse PA1 may be equal to the third width W3 of the second light pulsePA2. As depicted in FIG. 7, the first and second light pulse groups PG1and PG2 may each include more than two light pulses.

FIG. 4 shows a single light pulse, a width of which is modulated throughapplication of a modulation signal to the single light pulse of FIG. 2.

Referring to FIG. 4, the modulated light pulses MP1 and MP2 may have thecyclic characteristics of the light pulses P1 and P2 before modulation.However, the modulated light pulses MP1 and MP2 have a width W11 that issmaller than the first width W1 of the light pulses P1 and P2 beforemodulation. A ratio W11/W1 of the width W11 of the modulated lightpulses MP1 and MP2 with respect to the width Wlof the light pulses P1and P2 before modulation may be controlled according to the modulationsignal applied to the light pulses P1 and P2. The modulation signal maybe an electrical signal. The modulated light pulses MP1 and MP2 may havethe same height, that is, amplitude, as that of the light pulses P1 andP2 before modulation.

FIG. 5 shows light pulses modulated through application of a modulationsignal to the light pulses of FIG. 3.

Referring to FIG. 5, a first modulated light pulse group MPG1 includes afirst modulated light pulse MPA1 and a second modulated light pulseMPA2. The first modulated light pulse MPA1 and the second modulatedlight pulse MPA2 have widths smaller than those of the first and secondlight pulses PA1 and PA2 before modulation. The first modulated lightpulse MPA1 and the second modulated light pulse MPA2 have widthsdifferent from each other. The first modulated light pulse MPA1 and thesecond modulated light pulse MPA2 are separated from each other by asecond distance d2. The second distance d2 may be equal to or differentfrom the first distance d1 of FIG. 3. A second modulated light pulsegroup MPG2 may have the same modulated characteristics as those of thefirst modulated light pulse group MPG1.

FIG. 6 shows a magnified view of the first modulated light pulse groupMPG1 of FIG. 5.

Referring to FIG. 6, the first modulated light pulse MPA1 included inthe first modulated light pulse group has a width MW1 greater than awidth MW2 of the second modulated light pulse MPA2 included in the firstmodulated light pulse group MPG1, but the reverse is also possible. Ineither case, a ratio MW1/MW2 of the width MW1 of the first modulatedlight pulse MPA1 with respect to the width MW2 of the second modulatedlight pulse MPA2 may be constant in all of the modulated light pulsegroups MPG1 and MPG2. However, the ratio MW1/MW2 may be different ineach of a plurality of LiDAR devices 100.

FIGS. 7A and 7B show magnified views of the first modulated light pulsegroup MPG1 when the first light pulse group PG1 of FIG. 3 includes threelight pulses.

Referring to FIGS. 7A and 7B, gaps d3 and d4 between the first throughthird modulated light pulses MPA1 through MPA3 included in the firstmodulated light pulse group MPG1 may be equal or may be different fromeach other. For example, as depicted in FIG. 7A, the gaps d3 and d4between the first through third modulated light pulses MPA1 through MPA3may be equal to each other. As another example, as depicted in FIG. 7B,the gap d3 between the first modulated light pulse MPA1 and the secondmodulated light pulse MPA2 may be greater than the gap d4 between thesecond modulated light pulse MPA2 and the third modulated light pulseMPA3. In a case which is the reverse of FIG. 7B, the gap d3 may besmaller than the gap d4.

When more than two modulated light pulses are included in a modulatedlight pulse group, a width of at least one of the modulated light pulsesincluded in the modulated light pulse group may be different from widthsof the other modulated light pulses. Also, in this case, a ratio betweenthe widths of the modulated light pulses may be constant.

As an example, as depicted in FIG. 7A, when first through thirdmodulated light pulses MPA1 through MPA3 are included in the firstmodulated light pulse group MPG1, the width MW1 of the first modulatedlight pulse MPA1 may be greater than the widths MW2 and MW3 of thesecond and third modulated light pulses MPA2 and MPA3. The widths MW2and MW3 of the second and third modulated light pulses MPA2 and MPA3 maybe equal to each other.

As another example, as depicted in FIG. 7B, the widths MW1, MW2, and MW3of the first through third modulated light pulses MPA1 through MPA3 maybe different from each other.

In the case of FIG. 7A, a ratio MW1:MW2:MW3 of the widths MW1, MW2, andMW3 of the first through third modulated light pulses MPA1 through MPA3may be constant. Also, in the case of FIG. 7B, the ratio MW1:MW2:MW3 ofthe widths MW1, MW2, and MW3 of the first through third modulated lightpulses MPA1 through MPA3 may be constant. However, the ratio of thewidths MW1, MW2, and MW3 of FIG. 7A and the ratio of the widths MW1,MW2, and MW3 of FIG. 7B are different from each other.

FIG. 8 is a time chart showing time delays (or time differences) betweena light pulse emitted from the light-emitting unit 110 of FIG. 1 and amodulated light pulse received by the light-receiving unit 130 after thelight pulse has been reflected by the object 105. The emission of lightdue to a light emission operation of the light-emitting unit 110 may beimplemented by a light emission start signal provided from thecontroller 150 to the light-emitting unit 110. The light emission startsignal is provided to the light-emitting unit 110 and simultaneously amodulation start signal may be provided to the modulation unit 120 fromthe controller 150. In this way, a modulation signal may be applied tothe light-emitting unit 110 by the modulation unit 120. The lightemission start signal may be simultaneously provided to thelight-emitting unit 110 and the computation unit 140. In this way, thecomputation unit 140 may recognize a light emission start time t1. Whena modulated light pulse MP1 is received by the light-receiving unit 130,an electrical pulse signal, for example, a voltage pulse signal may begenerated by photoelectric conversion. The form of the electrical pulsesignal may be the same as that of the modulated light pulse MP1. Thegenerated electrical pulse signal is transmitted to the computation unit140, and the computation unit 140 may recognize, based on thetransmitted electrical pulse signal, a reception time t2 at which themodulated light pulse MP1 is received by the light-receiving unit 130.In this manner, after recognizing the emission start time t1 of themodulated light pulse MP1 and the reception time t2 of the modulatedlight pulse MP1, a time difference t241 between the two times t1 and t2is calculated. The calculation may be performed by the computation unit140, and a distance to the object 105 may be computed based on the timedifference. A light pulse DP different from the modulated light pulseMP1 emitted from the light-emitting unit 110 may be received by thelight-receiving unit 130. However, a width DW of the light pulse DP isdifferent from the width W11 of the modulated light pulse MP1 emittedfrom the light-emitting unit 110. Information about the width DW of thelight pulse DP is not provided to the computation unit 140 from thecontroller 150, and thus, the computation unit 140 does not measure atime delay (or a time difference) with respect to the light pulse DPreceived by the light-receiving unit 130.

Next, a method of operating the LiDAR device 100 according to anexemplary embodiment will be described with reference to FIG. 1.

FIG. 9 is a flowchart for explaining a method of operating the LiDARdevice 100, according to an exemplary embodiment.

Referring to FIG. 9, a first operation S1 of the method of operating theLiDAR device 100 is modulating light to be emitted by the light-emittingunit 110. The first operation (S1) is an operation of modulating a widthof a light pulse to be emitted from the light-emitting unit 110. Asdescribed with reference to FIG. 1, the modulation of the width of thelight pulse may be implemented by using a randomly generated look-uptable. Each of the LiDAR devices 100 may use a look-up table having asequence different from each other, and thus, each LiDAR device 100 mayimplement a unique modulation characteristic. Accordingly, even when aplurality of LiDAR devices 100 are simultaneously used in a space,crosstalk between the LiDAR devices 100 may be avoided. As anothermethod of modulating a width of a light pulse to be emitted, a uniquevalue given to the LiDAR device 100 is used as a parameter for lightpulse modulation. For example, when a modulation operation of a lightpulse is synchronized with a LiDAR GPS signal, random parameters may begenerated in real time, and thus, a light pulse may be modulated in realtime.

A light pulse to be emitted may be a single light pulse having a cycleas described with reference to FIG. 4, or, as described with referenceto FIGS. 5 through 7, the light pulse may be a first modulated lightpulse group MPG1 having a cycle and including a plurality of modulatedlight pulses.

A second operation (S2) of the method of operating the LiDAR device 100is emitting the modulated light towards the object 105. The object 105may be a fixed body or a moving body. The definitions of the fixed bodyand the moving body may be relative. For example, a body may be regardedas a fixed body or a moving body according to whether the LiDAR device100 is fixed or moving—i.e. according to whether the body is moving withrespect to the LiDAR device. Thus, even if both the object 105 and theLiDAR device 100 are moving, if the distance therebetween is maintainedconstant, the object 105 may be regarded as a fixed body. Also, in acase in which the object 105 is a fixed structure (for example, abuilding, a fence of a road, or an object dropped on a road) on theground but the LiDAR device 100 is moving, the object 105 may beregarded as a moving body with respect to the LiDAR device 100. Themodulation of light to be emitted (S1) and the emission of the modulatedlight to the object 105 (S2) are implemented when a light emission startsignal is provided to the light-emitting unit 110 by the controller 150and when a modulation signal is provided to the modulation unit 120 bythe controller 150. The light emission start signal and the modulationsignal are simultaneously provided. However, since the light pulseshould be emitted after modulation, the operations are therefore dividedinto the first operation (S1) and the second operation (S2).

A third operation (S3) of the method of operating the LiDAR device 100is receiving modulated light reflected by the object 105 from themodulated light emitted towards the object 105. The reception of themodulated light is implemented by the light-receiving unit 130.

A fourth operation (S4) of the method of operating the LiDAR device 100is measuring a time delay (a time difference) between a time when themodulated light pulse is emitted and a time when the modulated lightpulse is received. The measuring of the time difference in the fourthoperation (S4) is implemented in the computation unit 140. Thecomputation unit 140 considers a time when a light emission start signalprovided by the controller 150 is received as a light emission startingtime, and considers a time when a light reception signal of themodulated light pulse provided by the light-receiving unit 130 isreceived as a reception time of the modulated light. A modulationcharacteristic (for example, information about a width of the modulatedlight pulse) of the modulated light pulse that is generated by providinga light emission start signal to the light-emitting unit 110 andproviding a modulation signal to the modulation unit 120 by thecontroller 150 is provided to the computation unit 140 through thecontroller 150. Accordingly, among received signals provided through thelight-receiving unit 130, the computation unit 140 implements a timedifference measuring operation with respect to only a received signalcorresponding to the modulated light pulse emitted from thelight-emitting unit 110.

A fifth operation (S5) of the method of operating the LiDAR device 100is computing a distance to the object 105 by using the time differencemeasured in the fourth operation (S4). The distance to the object 105may be a distance between the object 105 and the LiDAR device 100. Thedistance information obtained in the fifth operation (S5) may be used tocontrol an operation of a device (for example, an autonomous drivingdevice) including the LiDAR device 100.

While one or more exemplary embodiments have been described withreference to the accompanying drawings, it will be understood by thoseof ordinary skill in the art that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Therefore, the scope of the inventive concept is defined notby the detailed description but by the technical scope defined by theappended claims.

What is claimed is:
 1. A light detection and ranging (LiDAR) devicecomprising: a light emitter configured to emit modulated light onto anobject, the modulated light including width modulation light of whichwidth is modulated depending on a width modulation signal; a lightreceiver configured to receive the modulated light reflected by theobject and generate a first reception signal based on the modulatedlight; and a processor configured to include a time-to-digital converter(TDC) measuring a time delay based on the first reception signal andcalculate a distance to the object based on the time delay measured bythe TDC.
 2. The LiDAR device of claim 1, wherein the modulated lightcomprises a modulated single light pulse.
 3. The LiDAR device of claim1, wherein the modulated light comprises a modulated light pulse group,and the modulated light pulse group comprises a plurality of modulatedsingle light pulses.
 4. The LiDAR device of claim 1, further comprisinga light modulation device configured to generate the modulated light. 5.The LiDAR device of claim 3, wherein the plurality of modulated singlelight pulses comprises a first single light pulse having a first width,a second single light pulse having a second width, different from thefirst width, and a third single light pulse having a third width,different from the first width and the second width, wherein a ratio ofthe first width to the second width is equal to a ratio of the secondwidth to the third width.
 6. The LiDAR device of claim 5, wherein a gapbetween the first single light pulse and the second single light pulseis equal to a gap between the second single light pulse and the thirdsingle light pulse.
 7. The LiDAR device of claim 5, wherein a gapbetween the first single light pulse and the second single light pulseis different from a gap between the second single light pulse and thethird single light pulse.
 8. An autonomous device comprising a lightdetection and ranging (LiDAR) device, wherein the LiDAR device includes:a light emitter configured to emit modulated light onto an object, themodulated light being modulated to have a first modulationcharacteristic; a light receiver configured to receive the modulatedlight reflected by the object and a plurality of other lights withouthaving the first modulation characteristic, generate a first receptionsignal based on the modulated light, and generate a plurality of otherreception signals based on the plurality of other lights; and aprocessor configured to identify the first reception signal as themodulated light that is emitted from the light emitter, based on thefirst modulation characteristic, and calculate a distance to the objectbased on the first reception signal without using the plurality of otherreception signals.
 9. An autonomous device comprising a light detectionand ranging (LiDAR) device, wherein the LiDAR device includes: a lightemitter configured to emit modulated light onto an object, the modulatedlight including width modulation light of which width is modulateddepending on a width modulation signal; a light receiver configured toreceive the modulated light reflected by the object and generate a firstreception signal based on the modulated light; and a processorconfigured to include a time-to-digital converter (TDC) measuring a timedelay based on the first reception signal and calculate a distance tothe object based on the time delay measured by the TDC.